Communications: radio wave antennas – Antennas – With vehicle
Reexamination Certificate
2000-09-05
2002-04-02
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
With vehicle
C343S703000, C343S850000
Reexamination Certificate
active
06366249
ABSTRACT:
TECHNICAL FIELD
This invention relates to a radio frequency antenna.
BACKGROUND OF THE INVENTION
Many communications systems for vehicles require an antenna mounted to the vehicle. For example, vehicle radios have conventional antennas, either fixed or retractable. Vehicle cellular communication devices often have a vehicle-mounted antenna.
It is known to mount radio or cellular antennas in or to a glass window of a vehicle. Certain glass-mounted antennas have impedance matching networks that have a low DC resistance to allow diagnostic detection of whether the antenna is properly connected to the cellular transceiver.
Referring to
FIG. 1
, the diagram illustrates the input impedance of an example quarter wave antenna
10
of a known type for receiving cellular communications to a vehicle. The input impedance is represented by a resistive component
12
in series with an active element
14
. The impedance Z
A
of the antenna is the sum of R
A
and X
A
, and is not suitable for provide a test signal to the antenna signal output because the antenna typically appears as an open circuit. Thus it is not possible for the transceiver to use a test signal to determine whether the antenna is connected to the transceiver.
FIG. 2
illustrates an example antenna
10
known in the art and includes an internal base
22
mounted on the interior side of a vehicle body member
27
(such as a planar or curved roof panel or glass windshield). On the exterior side of vehicle body member
27
is the external extending portion
20
of the antenna
10
. The external extending portion
20
is connected to the internal base
22
by a mounting screw (not shown) so that the two sandwich the vehicle body member
27
. An RF connector
24
for an antenna feed transmission cable (not shown) is connected through a radio frequency signal connection to the internal base
22
. An access hole
26
is provided opposite the mounting screw from the connector
24
. Within the internal base
22
are structures that are coupled to the antenna ground and signal output.
SUMMARY OF THE INVENTION
Advantageously, this invention provides an improved antenna suitable for mounting on a vehicle.
Advantageously, this invention provides an improved antenna that can be remotely monitored to ensure that it is correctly connected.
Advantageously, according to a preferred example, this invention provides a vehicle antenna comprising: an antenna structure having an input impedance, Z
A
, equal to a sum of a resistance and an active impedance; and a circuit element having high circuit element impedance at an operating frequency range of the antenna, wherein the circuit element is coupled in parallel with the input impedance.
REFERENCES:
patent: 4890116 (1989-12-01), Lewis
patent: 5111213 (1992-05-01), Jahoda et al.
Forest Daniel J
Jones Dennis P
General Motors Corporation
Simon Anthony Luke
Wimer Michael C.
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